


Never Letting You Go

by japanfan101



Series: Learning to Love the Void [3]
Category: Undertale (Video Game)
Genre: Other, Reader has no defined gender, Smut, Tentacles, Undertail, but reader has a vagina, goopy Gaster
Language: English
Status: Completed
Published: 2016-01-28
Updated: 2016-01-28
Packaged: 2018-05-16 20:12:21
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,306
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5839393
Author URL: https://archiveofourown.org/users/japanfan101/pseuds/japanfan101
Summary: <blockquote class="userstuff">
              <p>Goopy void Gaster and the reader get it on for the first time! Meant to be a sequel, but hey if you wanna jump right in, go for it. Let yourself be sucked into the void, don't resist ;)</p>
            </blockquote>





	Never Letting You Go

You were both uncertain at first, but that faded quickly; you desperately want Gaster, and he desperately wants you. The kiss he gives you is passionate, deep, and shortly after your lips meet his mouth you feel something… slimy poking at your lips. A tongue. Well… probably. You open up your mouth and allow his tongue to dance with yours as it explores your mouth, drawing a muffled moan out of your throat. The taste of black licorice coats your mouth and you press and rub your tongue against his to taste more.

He forms a few tentacles from his body, and holds your wrists and ankles gently, pressing you down into the bed and holding you there, making sure to not break the kiss. His tongue pushes deeper down your throat, almost making you gag, and yet it feels _so good_. Heat pools between your legs and you look at Gaster with half-lidded eyes, practically begging for… something, anything, you just want him and you want him now.

As you squirm in his grasp, you take note of the hungry look in his eyes. His body covers yours, the goop that makes up his body pressing against your skin and seeping through the gaps and holes in your clothes. It feels warm against your bare skin, causing you to flush and you groan around Gaster’s tongue. The dark, sticky liquid spreads over your entire body, enveloping you in a soothing heat that relaxes you. His hands fumble with your shirt and pants, you try to help him by pushing your body up off the bed some but the motion allows his body to fully wrap around you and hold you, suspended in the air. Your clothes fall onto the bed beneath you fairly quickly after that.

There’s nothing more you want right now than to feel him all over you, and inside you, and you try to tell him that but your speech comes out garbled, muffled, and incoherent. His hands roam over your body, but you’re held in place, and can’t move save for shuddering when he hits a particularly sensitive spot. You attempt to press your body upwards, into him, but his sticky body holds firmly and you whine, wriggling in his grasp.

Trapped in his body, you feel like millions of small, slimy hands are roaming over your body, touching and rubbing your skin, gripping you tightly, massaging you all over. Your skin prickles, so many different sensations are assaulting you at once and you can’t even beg for what you really want.

Gaster seems to get the picture though, either that or he’s also impatient, and a cold, bony finger presses against your entrance, contrasting with the warm liquid you’re covered in and the feeling makes you shiver under his touch. His tongue pulls out of your mouth and you take in a deep gasp of air, but as he gently rubs circles against your clit and heat courses through your veins, the gasp becomes a surprised, pleased cry.

“G… Gaster,” you moan, “please, I want more, I want you so bad!” His face flushes grey and he quickly presses his mouth against your neck, nipping lightly and then licking the area. A whimper pours out of your mouth, “please…”

He bites your neck once more, slightly harder this time, and simultaneously pushes his finger inside of you. Biting your bottom lip, you try hard to keep quiet, but he puts a stop to that by running his thumb across your bottom lip and pushing it in your mouth softly, pulling your mouth open and then removing his thumb. Clearly he doesn’t want you to hold back, and you’re slowly losing yourself in the feelings which makes it hard to try and stay silent anyways.

Your head falls back as he presses his finger deeper inside you. Soon he’s thrusting his finger in and out, slowly at first but as he picks up his pace your ragged breathing and gasps turn to moans. When he curls his finger inside you and manages to rub against the spot that has you crying out, you press your hips against his finger desperately, panting and trying to feel more of him. Your mind starts to go numb, “M-more, please, I need more of you, Gaster…” He obliges, pressing two more fingers inside of you and curling them to hit and massage that same spot.

You feel some of the goop from his body join his fingers, and it expands slowly inside of you, filling you up and making you quiver in his grasp. His teeth graze over your collarbone and he pulls his fingers out of you, but the goop left is still expanding as much as it can without hurting you. You take quick, shaky breaths, it feels like you’re melting together with Gaster and you love every second of it. Your entire body is flushed, and you can hear your heart pounding in your ears.

Gaster’s finger continues to massage your clit slowly, but insistently, and you feel sparks of electricity shoot through you as you desperately press up into him, incoherently begging for more between the rough gasps and moans he’s drawing out of you.

Impatiently, you try to push yourself against him and groan. The feeling of him inside of you, so warm and full, but not moving is driving you crazy, and you can’t help but feel like he’s teasing you. “P-please...” When he does start to move, the feeling is far different from anything you’ve felt before. It feels like he’s wriggling deep inside of you more than anything, rubbing against all your most sensitive spots as he slowly moves in and out. Your breathing comes out in gasps. When he presses his mouth against yours again and his tongue explores deep inside your mouth again, you’re taken by surprise. It’s not an unwanted intrusion, though, and you suck lightly on his tongue, humming.

Shortly after, when you’ve gotten used to the feeling, he picks up the pace sending jolts of pleasure coursing through you, his tongue muffling your cries. Your hips buck wildly as much as they can in the sticky mess of his body, pulling him deeper inside you every time he presses back in.

His thrusts become more and more erratic and your mind slowly melts away, drowning in the overwhelming pleasure. Your body heats up and your cries get louder, though his tongue keeps you from getting too loud. Unable to help yourself, your eyes shut and you try to grind your hips into him. It doesn’t work all that well, and you groan in a mix of frustration and pleasure, desperate for more of him.

The finger working your clit presses down harder, almost painfully, and you jump in his grasp. It only takes a few more minutes of this to push you over the edge, nearly pulling a scream from your mouth as your vision fades to white. Gaster slows his hand and eventually stops and pulls it away, but continues thrusting in and out of you. Your body goes numb and your eyes flutter shut as he cums a few moments later, and you feel a warm liquid flood inside of you.

A sigh escapes your lips and Gaster gently puts you back on the bed, releasing your limbs and pulling his tongue out of your mouth. You take a deep breath in, gasping. After a bit of rest he pulls out of you completely and practically collapses next to you, pulling you close against him.

You mumble that you love him as you pass out with a dreamy smile on your face, too spent to even try and keep your eyes open. The last thing you feel before drifting off is his hand as it brushes through your hair softly.

**Author's Note:**

> So I wanted to write sexy goopy Gaster and I wound up with this. So. Wanted it to be super passionate and stuff, because hey, it's been a long time since /either/ of the characters got laid and they both have been craving the physical contact. Feel free to let me know if you liked it, or hated it, and why~ I'm always looking to improve. 
> 
> This is my first smut that's not soul sex and while I'm happy with it, I'm also really nervous posting it honestly.


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